Video encoders may be used to compress video signals prior to transmission and/or storage in order to reduce the bandwidth and/or memory space requirements of the video signals. For example HEVC (High Efficiency Video Coding, e.g., H.265 Series H: Audiovisual and Multimedia Systems, Infrastructure of audiovisual services—Coding of moving video, Telecommunication Standardization Sector of ITU, April 2013) may divide each frame of a video signal into a 64×64 pixel element/pel coding block (CB), recursively decide whether to process the coding block as a 64×64 coding unit (CU) or split the coding block into smaller coding units (e.g., 32×32, 16×16, etc.), and select an encoding mode that attempts to minimize the cost of compression (e.g., compression ratio, encoding time).
The encoding mode may generally be either an inter prediction mode that references data (e.g., motion vectors) from other frames or an intra prediction mode that references data (e.g., neighboring pixels) from within the current frame. Inter prediction may be effective when the scene of a video has not changed much from previous frames. Intra prediction, on the other hand, may be more effective when the scene in the current frame has changed from previous frames. The decision whether to split the coding block may involve recursively applying both an intra prediction coding stage and an inter prediction coding stage to the coding units in order to determine the appropriate unit size based on the relative cost of compression between the two encoding modes. Applying the intra prediction coding stage to the coding units on each pass of the split decision, however, may unnecessarily increase encoding time, particularly for video signals in which scene changes are infrequent and intra prediction is not likely to be selected as the encoding mode.